The announcement in August of a new commercial test for Alzheimer's disease risk has prompted more public health experts to call for special legal protection of genetic information.

The test, marketed by Athena Neurosciences Inc., detects the presence of the apolipoprotein E (APO-E) gene in the DNA of a patient's blood cells. But the scientific community has not reached consensus on the meaning of a "positive test." Not everyone with the gene will develop Alzheimer's disease, and not everyone with Alzheimer's disease carries the gene.

Because the results of the test may be ambiguous, P&S researchers argue that apolipoprotein E genotypes should not be available to third parties, such as insurers or employers, until genotypic risks are fully understood.

"This test is not like an HIV test or a Huntington's disease gene test," says Dr. Richard Mayeux, the Gertrude H. Sergievsky Professor of Neurology, professor of psychiatry and public health, and internationally recognized expert on the epidemiology of Alzheimer's disease. "If you test positive for HIV, you'll eventually develop AIDS. If you test positive for the Huntington's disease gene, you are going to develop Huntington's disease. But the APO-E test is inconclusive. This country spends $70 million a year caring for people with Alzheimer's disease. The temptation may exist for employers or insurers to use the APO-E test to avoid hiring or insuring people who have the gene, even though they may never develop the disease."

Research by Dr. Mayeux, director of the Sergievsky Center at Columbia-Presbyterian Medical Center, confirmed the suspected link between the apolipoprotein E gene and increased risk of Alzheimer's disease.

Dr. Mayeux and his colleague Dr. Nicole Schupf wrote in the September issue of the American Journal of Public Health that "many people with this gene may never develop the disease. Thus, while the apolipoprotein genotype may be undeniable as a genetic risk factor for Alzheimer's disease, it does not provide sufficient information to be an adequate predictive genetic test."

To protect individuals from being stigmatized by employers, health insurers, colleagues, or family based on results of ambiguous genetic testing, Dr. Mayeux and Dr. Schupf call for legal protection of each individual's genetic code and the establishment of policies to regulate access to genetic information.

Federal legislation that would limit access to genetic information is under consideration.

"Agencies and public health groups are beginning to undertake a detailed review of these troubling questions, but time is not on their side," say Dr. Mayeux and Dr. Schupf. "The rapid pace of scientific progress in molecular medicine suggests that all investigators concerned with public health questions should carefully consider the issue raised by this remarkable era of scientific progress."